ups <-> psu comms

Is there such a thing as a ups to power supply communications channel over the 240V lines, such that the UPS can talk to each power supply in a server and figure out what is plugged in where? It seems such an obviously useful idea but I can't see that such a thing exists anywhere. Comms would only need to be very basic (hundreds of bps would be sufficient) - PSU would tell the UPS what its maximum rating was and maybe an identifier (eg for grouping redundant PSUs), and the UPS would tell the PSU when it was on battery etc. I'm shopping for UPS's and looking at features etc. I'm opting for network based comms on my UPS's these days but even seems like a lot more mucking around than it could be. James